1. Technical Field
The present invention relates to outer rotor-type rotating electric machines that include a rotor, which has magnets circumferentially extending and being radially magnetized, and a stator disposed radially inside the rotor.
2. Description of Related Art
Rotating electric machines that include a stator (or armature stator) and a rotor (or field rotor) can be classified into inner rotor-type machines in which the rotor is disposed radially inside the stator and outer rotor-type machines in which the rotor is disposed radially outside the stator.
The outer rotor-type rotating electric machines were originally considered to be higher in performance because they have high-output elements such as higher winding performance and ease in arranging field magnets and securing core magnetic flux passages.
Japanese Patent Application Publication No. JPH10178753A discloses a rotor for a small-sized motor that is of an outer rotor type. The rotor includes a magnetic frame and a yoke which are formed of laminated plates to have a high damping coefficient against shocks.
However, in practice, the conventional outer rotor-type rotating electric machines, including the motor disclosed in the above patent document, are inferior in performance to the inner rotor-type rotating electric machines. Therefore, the outer rotor-type rotating electric machines have hardly been used practically in industry.